The present invention relates to a photograph printing method for printing on a photograph printing paper a plural number of frames on a film recorded images by a camera.
An auto printer, which automatically prints images recorded on a film on a photograph printing paper, measures separately an amount of light from each frame of a film, and calculates an integral transmission density of the entire surface of each frame on the basis of the results of this measurement. The printer applies correction processes, such as the slope control and the color correction (color control), based on the difference between the integral transmission density and a reference density ( the density of a called typical negative). The quantity of the print exposure (referred frequently to as a print exposure quantity) is determined every image. The printer prints the images of the frames on a photograph printing paper at the determined print exposure quantity. The resultant prints are proper in density and well color balanced since a variation of exposures and color failures, which would take place in the stage of photographing, are corrected through the above process. The average value of integral transmission density values of a number of images may be often used as the reference density. On the other hand, an image average density may be used instead of the integral transmission density.
When comparatively observing the images formed by taking photographs of similar scenes plural times by a camera, it is seen that the densities, colors, and the like of the major subjects are little changed, but differences are often observed in the relative areas of the background in the images because of different compositions of the scenes. The change of the relative area of background results in change of the average density and the color balance of the entire image. The auto printer determines the exposure conditions on the basis of the average density of the image surface. Accordingly, in the prints of the images of similar scenes produced by the auto printer, the densities and the color balance of major subjects are greatly influenced by the changed relative area of background and so change. The nonuniform finishing of the prints of the images of the same scenes gives a user a feeling of mental difference.
Solutions of this problem have been proposed in Published Unexamined Japanese Patent Application Nos. Sho. 54-26729, 56-153334, 63-80242, 63-80244, and the like. In those proposed techniques, an image is divided into a number of segmental areas. The intensity of light from the segmental areas are measured. Comparison is made of the density values (e.g., average values, maximum values, and minimum values) of the image areas (e.g., central area and peripheral area), the ratios of the bright and dark areas, color distributions, and the like. If the two images compared are similar in the density values, the area ratios, and the color distributions, it is assumed that the images are formed by taking photograph of the same scene. Those images are printed under the equal or similar printing conditions.
In some types of cameras, an optimum exposure is automatically determined by a called multiple photometric method (also called a division photometric method, an evaluation photometric method, a multi-pattern photometric method or a multi photometric method) in which different areas on a subject to be photographed are measured the amount of light by using a plural number of photometric elements. Many and various technical improvements have been actively made in those cameras (Published Unexamined Japanese Patent Application Nos. Sho. 57-42026, and Hei. 1-280737 and 2-84628).
When the density values, the area ratios, and the color distributions are greatly different between the compared images, the proposed technique fails to make the assumption that the images are formed by taking photographs of similar scenes. It is difficult to produce the prints finished such that the major subjects of the images are substantially equal.
In the images formed by taking photograph of similar scenes, it is not seldom that the density values, the area ratios, and the color distributions are greatly different. When an image formed by taking photograph of a scene by an auto focus camera after the focus lock without changing its composition is compared with an image formed by taking photographs of the same scene after the composition is changed, the density value and the ratio of the bright and dark areas are greatly different between those images. Where the stroboscopic light is used for photographing a scene, when the composition of the scene is slightly changed, a portion in the image where a maximum density is present changes. Thus, when using the conventional technique, it is difficult to print the film images of the same scene so as to be uniform in their finishing.
Further when a film bearing images photographed by the camera of the type in which the quantity of exposure light is automatically determined is set to the auto printer and printed, since the print exposure quantities for the frames are determined on the basis of the integral transmission density values of the images, the print exposure quantities, excessively corrected are set up for the frames with less varied exposures, so that the print of improper density is frequently formed. Particularly in the camera of the type in which the exposure control is locked when the camera is focused on the major subject, the image is photographed at the exposure set for the major subject. Accordingly, a small quantity of correction is required for the nonuniformity of the exposure. However, the auto printer is incapable of discriminating the major subject. The printer obtains the print exposure quantity on the basis of the integral transmission density in a manner as described above. The integral transmission density is influenced by a density of the background. Where the background density is high, the exposure is determined to be overexposure. An excessive correction is made so as to increase the print exposure quantity. As a result, the density of the major subject of the finished print is higher than an expected one.
To cope with the problem, the Applicant of the present Patent Application proposed the invention comprising the steps of measuring light intensity of a plural number of frames, obtaining a print exposure quantity on the basis of the results of the measuring step, and printing the frames on a printing paper at the thus obtained print exposure quantity (in Japanese Patent Application Hei. No. 3-88456).
The invention of Japanese Patent Application No. Hei. 3-88456 succeeds in solving the above problem, and can produce prints of proper density at higher probability than the conventional technique. From the subsequent study of the inventors of the present Patent Application, it is found that in the invention of Japanese Patent Application No. Hei 3-88456, the print colors are influenced by various parameters, such as film type, film nonuniformity caused in the manufacturing stage, photographing light source, film aging, film characteristics caused by the storage of films, development nonuniformity, and the like. The prints of poor color control (color NG print) are formed at higher probability than by the conventional technique.